Enough of them might, if Hussein steps aside and strongly endorses Hillary. It will be a deal worked out in advance.
I come from a large family of black Democrats. Trust me. They won't believe a word of it, and will boycott the election. It'll create a war within the party like nothing you've ever seen.
There's only one scenario under which blacks would overwhelmingly give Hillary their support in 2012, but I'll leave it to you to fill in the blanks.